Too much slapdash raunchiness and not enough sweetness is how best to describe "Hot Tub Time Machine," a hit-and-miss goofball comedy well aware of how silly it is. The on-the-nose title alone proves that all involved aren't exactly taking things seriously, instead out to just make a fun, undemanding party movie. Director Steve Pink (2006's "Accepted") and screenwriters Josh Heald, Sean Anders and John Morris succeed some of the time, but are just as often running on autopilot and not going far enough to explore its comedically-loaded premise.

When their wayward buddy Lou (Rob Corddry) narrowly survives what may or may not have been a suicide attempt—he was in his garage pumping the gas and breathing in the exhaust as he drank and sang his way through Motley Crue's "Home Sweet Home"—it is a reminder to the recently separated Adam (John Cusack) and cheated-on Nick (Craig Robinson) that none of their lives have turned out how they expected. In an effort to recapture their care-free college days, the three of them, along with Adam's 20-year-old slacker nephew Jacob (Clark Duke), head to Kodiak Valley, a ski resort town they vacationed at decades earlier. They are at first dismayed to find the place is now a dump, but a night of heavy alcohol consumption and hot tub debauchery leads to a crack in the time-space continuum. Now they're back at Winterfest 1986, reliving their past experiences with the threat that one small change in what originally happened could alter their 2010 present day. This proves particularly alarming for Jacob, stuck in a calendar year that predates his birth.

With the exception of a few movie references—the dialogue and one-sheet from 1984's "Red Dawn" is recalled; a romantic scene is staged to mimic 1984's "Sixteen Candles," and go-to '80s bad guy William Zabka (1984's "The Karate Kid") gets a familiar sort of role—and a handful of time-specific jokes (one girl asks what e-mail is, while a walk-on character carries a cell phone the size of a large brick), "Hot Tub Time Machine" really doesn't take satisfactory advantage of its time-travel storyline. There are a fair amount of classic tunes from the decade, to be sure, and part of the setting revolves around a Poison concert, but director Steve Pink primarily focuses on gags that could just as easily have taken place in modern times. Some work—an ongoing joke involving a cheerful bellhop (Crispin Glover) destined to lose his arm in a freak accident at any moment gets funnier the longer it plays out, and a mystical repairman's (Chevy Chase) repeated mistaking of Jacob as a "young lady" gets a laugh or two—but the majority are of a cruder, more predictable nature. Comic bits involving three-ways, oral sex, bodily fluids and heavy amounts of hard drugs feel old and musty and the one-time shock value of such material no longer exists.

Not so much a tightly woven story as it is a series of sketches and set-pieces stitched together to form a mildly coherent narrative, the film tends toward broad characterizations and a free-wheeling side that could just as easily be considered sloppy. Further adding to the superficiality are some chintzy-looking production values and cheap interior sets. Not only have the quartet of men gone back to 1986, it actually looks like they've entered a direct-to-video movie made in 1986. With vulgarity invading most scenes, it is a welcome respite that some quieter levity be brought to the proceedings by way of Adam's romance with fun-loving Spin journalist April (Lizzy Caplan), in town to cover the Poison concert. Their scenes are fleeting, but there is a sweetness to them that the rest of the movie sorely needed. More could have been done, for example, with Jacob's meeting of his own mother (Collette Wolf) when she was his age, but it, too, is treated as no more than a punchline when she first lays eyes on him and labels him a dork.

The cast looks to be having a ball, at least. Rob Corddry (2008's "Harold & Kumar Escape from Guantanamo Bay"), as the wild, up-for-anything Lou, is an uninhibited treat to watch, playing the kind of guy who never grew up and has always longed to stay twenty-one. Craig Robinson (2009's "Miss March") gets some good moments, none better than when he calls up his wife (only nine years old in 1986) and berates her for cheating on him. Clark Duke (2008's "Sex Drive") is adorable as Jacob, a devilish glint in his eye and a talent of comic timing. John Cusack (2009's "2012") is the straight man of the group, but that's needed, and he can pretty much do no wrong. Memorable smaller performances go to Lyndsy Fonseca (TV's "How I Met Your Mother"), as Adam's party-hard '80s girlfriend Jennie Steadman; Crispin Glover (2010's "Alice in Wonderland"), stealing scenes as bellhop Phil, and Lizzy Caplan (2008's "Cloverfield"), making the most of April, the movie's central love interest. Striking the one clear false note is Chevy Chase (2006's "Zoom"). It isn't his fault that his bizarre, undernourished role as the repairman is such a miscalculation, but it also doesn't cast him in his brightest light.

Watching "Hot Tub Time Machine" is diverting enough as it plays out. Cast aside the ridiculous concept that a hot tub is a time-traveling portal and a particular energy drink is its elixir and some enjoyment can be had. Lightly peppered with humorous bits, there are no uproarious moments but there are quite a few gags that fall flat. What's missing is a much-needed heart. Director Steve Pink is so gung-ho about showing off the next gross-out trick up his sleeve that he forgets to even it out with more innately human elements and relationships that run deeper than on the surface. One walks out of the film not exactly displeased, but certainly left wanting and wishing for more than just a disposable time-waster.